Generally, portable circular saws include a housing enclosing an electric motor therein, a handle carried by the housing, a circular saw blade operatively connected to the electric motor, a blade case fixed to the housing and adapted to enclose substantially the upper half of the saw blade, a shoe for supporting the housing thereon, and a cover pivotally mounted on the housing and adapted to cover substantially the lower half of the saw blade projecting from the base plate. One common arrangement for portable circular saws is the "spur gear" circular saw. In such circular saw, the motor drive rotation axis is coincident or substantially parallel to the blade rotation axis. One such circular saw is shown in U.S. Pat. No. 5,561,907.
Another common arrangement for portable circular saws is the worm drive circular saw 100, as shown in FIG. 1. Unlike the spur gear circular saw, the motor axis 261 is substantially perpendicular to the blade rotation axis 262. In addition, the worm drive saw has an elongated housing 26 enclosing the motor. The main handle 263 is located at the end of the motor housing.
Traditionally, a worm gear transmission is used to operatively connect the motor to the blade drive shaft perpendicularly rather than in parallel. However, bevel gear transmissions are also used for the same purpose. Nevertheless, people still call saws with bevel gear transmissions "worm drive saws".
A worm drive saw is preferred over spur gear saws by some users because the housing is longer and narrower than a spur gear saw. The longer housing is desirable for some applications, such as construction of wooden frames, roofs, ceilings, floors, etc., that require a longer housing to reach the workpiece.
The present invention offers two distinct advantages over the prior art worm drive saw. The first is improved balance and maneuverablility by locating the center of gravity closer to the main handle.
The second addresses the condition that the motor axis is in the prior art generally coaxial to the user's arm when holding the saw by the main handle. The present invention effects improved handling by changing the handle position.
Improved user handling is also accomplished by modifying the prior art transmissions. FIG. 2 shows a prior art transmission. The motor 15 has a drive shaft 25 connected to a gear 251. This gear 251 meshes with a bevel gear 31, which in turn is fixed to an arbor 21, which drives the blade 28 in a clockwise direction X, as is necessary for cutting. The bevel gear 31 is located to the left of the drive shaft 25. In other words, the distance between the blade 28 and the bevel gear 31 is substantially equal to or less than the distance from the blade 28 to the drive shaft 25 providing a transmission of less weight and smaller size. However, the drive shaft rotates in a counterclockwise direction 17 and creates a clockwise direction X, creating a clockwise reaction torque 27.
It is also known in the prior art to provide a hanger on a circular saw for hanging the saw from a joist where there are no table-like supports and the saw is not in use. Prior art hangers have been proposed to orient the main handle vertically upward for easy accessibility, but they increase the width or height of the saw. See, e.g., U.S. Pat. Nos. 2,841,192 and 4,406,064.